Final answer:
Sea stars have a larval stage called a bipinnaria, which undergoes metamorphosis to become a juvenile sea star with pentaradial symmetry.
Step-by-step explanation:
Sea stars, also known as starfish, have a unique larval stage called a bipinnaria. The bipinnaria larva has a bilateral symmetry with cilia on its surface that help it to swim in the water. As the larva grows, it undergoes metamorphosis and transforms into a juvenile sea star with its characteristic pentaradial symmetry.